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Title: Latent image exposure monitor using scatterometry

Abstract

We discuss the use of light scattered from a latent image to control photoresist exposure dose and focus conditions which results in improved control of the critical dimension (CD) of the developed photoresist. A laser at a non-exposing wavelength is used to illuminate a latent image grating. The light diffracted from the grating is directly related to the exposure dose and focus and thus to the resultant CD in the developed resist. Modeling has been done using rigorous coupled wave analysis to predict the diffraction from a latent image as a function of the substrate optical properties and the photoactive compound (PAC) concentration distribution inside the photoresist. It is possible to use the model to solve the inverse problem: given the diffraction, to predict the parameters of the latent image and hence the developed pattern. This latent image monitor can be implemented in a stepper to monitor exposure in situ, or prior to development to predict the developed CD of a wafer for early detection of bad devices. Experimentation has been conducted using various photoresists and substrates with excellent agreement between theoretical and experimental results. The technique has been used to characterize a test pattern with a focused spot asmore » small as 36{mu}m in diameter. Using diffracted light from a simulated closed-loop control of exposure dose, CD control was improved by as much as 4 times for substrates with variations in underlying film thickness, compared to using fixed exposure time. The latent image monitor has also been applied to wafers with rough metal substrates and focus optimization.« less

Authors:
; ; ; ; ;  [1]; ;  [2]
  1. New Mexico Univ., Albuquerque, NM (United States). Center for High Technology Materials
  2. Sandia National Labs., Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10174068
Report Number(s):
SAND-92-0971C; CONF-9203177-2
ON: DE92019427
DOE Contract Number:  
AC04-76DP00789
Resource Type:
Conference
Resource Relation:
Conference: International Society for Optical Engineering (SPIE) symposium on microlithography,San Jose, CA (United States),8-13 Mar 1992; Other Information: PBD: [1992]
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 47 OTHER INSTRUMENTATION; 36 MATERIALS SCIENCE; PHOTORESISTORS; LIGHT SCATTERING; MONITORING; LASER RADIATION; DIFFRACTION GRATINGS; IMAGES; QUALITY CONTROL; ALUMINIUM; DEFECTS; SURFACE PROPERTIES; 426000; 440600; 360104; COMPONENTS, ELECTRON DEVICES AND CIRCUITS; OPTICAL INSTRUMENTATION; PHYSICAL PROPERTIES

Citation Formats

Milner, L M, Hickman, K C, Gaspar, S M, Bishop, K P, Naqvi, S S, McNeil, J R, Blain, M, and Draper, B L. Latent image exposure monitor using scatterometry. United States: N. p., 1992. Web.
Milner, L M, Hickman, K C, Gaspar, S M, Bishop, K P, Naqvi, S S, McNeil, J R, Blain, M, & Draper, B L. Latent image exposure monitor using scatterometry. United States.
Milner, L M, Hickman, K C, Gaspar, S M, Bishop, K P, Naqvi, S S, McNeil, J R, Blain, M, and Draper, B L. 1992. "Latent image exposure monitor using scatterometry". United States.
@article{osti_10174068,
title = {Latent image exposure monitor using scatterometry},
author = {Milner, L M and Hickman, K C and Gaspar, S M and Bishop, K P and Naqvi, S S and McNeil, J R and Blain, M and Draper, B L},
abstractNote = {We discuss the use of light scattered from a latent image to control photoresist exposure dose and focus conditions which results in improved control of the critical dimension (CD) of the developed photoresist. A laser at a non-exposing wavelength is used to illuminate a latent image grating. The light diffracted from the grating is directly related to the exposure dose and focus and thus to the resultant CD in the developed resist. Modeling has been done using rigorous coupled wave analysis to predict the diffraction from a latent image as a function of the substrate optical properties and the photoactive compound (PAC) concentration distribution inside the photoresist. It is possible to use the model to solve the inverse problem: given the diffraction, to predict the parameters of the latent image and hence the developed pattern. This latent image monitor can be implemented in a stepper to monitor exposure in situ, or prior to development to predict the developed CD of a wafer for early detection of bad devices. Experimentation has been conducted using various photoresists and substrates with excellent agreement between theoretical and experimental results. The technique has been used to characterize a test pattern with a focused spot as small as 36{mu}m in diameter. Using diffracted light from a simulated closed-loop control of exposure dose, CD control was improved by as much as 4 times for substrates with variations in underlying film thickness, compared to using fixed exposure time. The latent image monitor has also been applied to wafers with rough metal substrates and focus optimization.},
doi = {},
url = {https://www.osti.gov/biblio/10174068}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Sep 01 00:00:00 EDT 1992},
month = {Tue Sep 01 00:00:00 EDT 1992}
}

Conference:
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